Evidence map›Paper›PMID 32973285›Full record

ArticleScientific reports2020

Efficacy of masks and face coverings in controlling outward aerosol particle emission from expiratory activities.

Sima Asadi, Christopher D Cappa, Santiago Barreda, Anthony S Wexler, Nicole M Bouvier, William D Ristenpart

Open access · goldAbstract read
PubMed Full text at PMC Publisher
In one paragraph

Article in Scientific reports, 2020. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 163 papers, 9 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
163citing papers in PubMed, 9 pooled it
56.7field-weighted citation impact, top 1% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

163 citing papers in PubMed, 9 syntheses or guidelines pooled it, 515 citations in OpenAlex.

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  17. Risks and benefits of face masks in children.Frontiers in pediatrics · 2026
    Review
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  20. Article

103 more citing papers are in PubMed but not listed here.

4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

6 authors at 3 institutions in 1 country.

Sima AsadiDepartment of Chemical Engineering, University of California Davis, 1 Shields Ave, Davis, CA, 95616, USA.
Christopher D CappaDepartment of Civil and Environmental Engineering, University of California Davis, 1 Shields Ave, Davis, CA, 95616, USA.
Santiago BarredaDepartment of Linguistics, University of California Davis, 1 Shields Ave, Davis, CA, 95616, USA.
Anthony S WexlerDepartment of Civil and Environmental Engineering, University of California Davis, 1 Shields Ave, Davis, CA, 95616, USA.
Nicole M BouvierDepartment of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY, 10029, USA.
William D RistenpartDepartment of Chemical Engineering, University of California Davis, 1 Shields Ave, Davis, CA, 95616, USA. wdristenpart@ucdavis.edu.
University of California, Davis · USIcahn School of Medicine at Mount Sinai · USQuality Research · US

Funding

Quantifying Environmental Variables Affecting Airborne Influenza TransmissionR01AI110703 · NIAID · ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI · PI BOUVIER, NICOLE M. · 2015 to 2019
$2.0M
NIAID NIH HHS R01 AI110703
6 · The paper itself

Abstract

The COVID-19 pandemic triggered a surge in demand for facemasks to protect against disease transmission. In response to shortages, many public health authorities have recommended homemade masks as acceptable alternatives to surgical masks and N95 respirators. Although mask wearing is intended, in part, to protect others from exhaled, virus-containing particles, few studies have examined particle emission by mask-wearers into the surrounding air. Here, we measured outward emissions of micron-scale aerosol particles by healthy humans performing various expiratory activities while wearing different types of medical-grade or homemade masks. Both surgical masks and unvented KN95 respirators, even without fit-testing, reduce the outward particle emission rates by 90% and 74% on average during speaking and coughing, respectively, compared to wearing no mask, corroborating their effectiveness at reducing outward emission. These masks similarly decreased the outward particle emission of a coughing superemitter, who for unclear reasons emitted up to two orders of magnitude more expiratory particles via coughing than average. In contrast, shedding of non-expiratory micron-scale particulates from friable cellulosic fibers in homemade cotton-fabric masks confounded explicit determination of their efficacy at reducing expiratory particle emission. Audio analysis of the speech and coughing intensity confirmed that people speak more loudly, but do not cough more loudly, when wearing a mask. Further work is needed to establish the efficacy of cloth masks at blocking expiratory particles for speech and coughing at varied intensity and to assess whether virus-contaminated fabrics can generate aerosolized fomites, but the results strongly corroborate the efficacy of medical-grade masks and highlight the importance of regular washing of homemade masks.

Indexed as

MasksRespiratory Protective DevicesAdolescentAdultAerosolsBetacoronavirusCoronavirus InfectionsCoughCOVID-19ExhalationFemaleFiltrationHumansInhalation ExposureMaleMiddle AgedAerosols

Identifiers

PMID32973285
PMCPMC7518250
OpenAlexW3088267014

What OpenQuestion holds

Textmetadata
LicenceCC BY
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.